This invention relates generally to trailers and pulling vehicles and, in particular, to trailers interconnected by way of a king-pin plate and means for locking the trailer in a non-articulating configuration while allowing the king-pin plate to pivot.
Vehicles with articulating trailers may be quite difficult to operate in reverse without assuming unworkable or even jack-knife situations. The problem becomes much more pronounced when additional points of articulation are added. For example, in tandem configurations interconnected by a converter dolly or xe2x80x9cjoe-dog,xe2x80x9d three points of articulation may be created, exacerbating the problem. These four parts of articulation include the first king-pin plate or fifth-wheel interconnection between the tractor and first trailer, a second part of articulation between the back of the first trailer and the forward hitch of the converter dolly, and the king-pin plate or fifth-wheel interconnection between the dolly and the front of the rearward trailer. In situations such as these, it is very difficult to back up the rig without odd or unpredictable accordion action taking place.
As a consequence, various devices have been engineered to lock points of articulation to bring about a more controlled movement. In certain commercially available configurations, an extensible pin is located forwardly or rearwardly of the king-pin plate, but on the king-pin plate itself. While this allows the king-pin plate to pivot with respect to a pivoting axis situated transverse to the direction of vehicle movement, problems may arise when driving over, or backing up, on pronounced inclines, in which case the pin is substantially pulled out of the aperture used to engage the pin in its extended position. If the vehicle is turned with this pin extracted, a strong moment may be exerted on the pin, shearing it off.
Other attempts at solving this problem have used pins oriented along the pivotal axis of the king-pin plate, but the pins are mounted on the plate itself, which creates other problems. In U.S. Pat. No. 5,456,483 to Madsen et al, for example, two retractable pins (22) are mounted on the king-pin plate itself, and very near to the plate center. This configuration is deficient for at least two reasons. Firstly, the manufacturers of king-pin plates typically specify that no modification should be done to the plate which could cause operational problems. Modification of the plate itself also forces replacement of the entire king-pin plate in the event of shearing or malfunction. But in addition, with respect to design of the ""483 patent in particular, the pins are too close to the center pivot point, such that the forces on the pins themselves would be very large, as are the forced applied to the fore and aft rocking pins of the king-pin plate.
U.S. Pat. No. 4,775,165 to Grovum teaches an apparatus very similar to that set forth in the ""483 patent, except that the retractable pins are mounted on side panels, also attached to the king-pin plate itself. Again, direct attachment to the king-pin plate is less than optimal for this purpose. U.S. Pat. No. 5,098,115 to Haire et al utilizes retractable pins forwardly of the king-pin plate, but, once again, mounted directly thereon. Although this allows the pivot king-pin plate to continue its pivoting action as the trailer moves over inclined surfaces, mounting to the king-pin plate creates potential problems with manufacture and maintenance, if not with safety.
The present invention resides in a locking mechanism for an articulating trailer of the type which couples to a king-pin plate, and improves upon the existing art by providing a arrangement for locking the trailer in a non-articulated position while allowing the king-pin plate to continue pivoting.
In a preferred embodiment, one or more apertures are formed on one of the trailer and the trailer-pulling unit, and one or more powered locking members are disposed on the other of the trailer and trailer-pulling unit. Each member is moveable between an extended position, wherein it engages with a respective aperture, and a retracted position, wherein the member is disengaged from the aperture.
Importantly, each member is positioned along a line parallel to the axis about which the king-pin plate pivots, enabling the plate to continue pivoting even when the members are extended. The aperture is also preferably oval shaped to allow for unimpeded pivoting of the trailer attached to the king-pin plate while the locking member is engaged within the aperture.
In the preferred embodiment, the aperture is formed on the trailer, and the powered locking member is supported on the trailer-pulling unit. In addition, two sets of powered locking members and associated apertures are preferably used, one set on either side of the king-pin plate. The locking member is preferably pneumatically powered, though hydraulic, mechanical or other alternatives may be employed.
The invention is applicable to a variety of implementations, including roll-off type trailers and dump trailers using joe-dog configurations.